A number of different circuit arrangements for PFC (Power Factor Correction) booster circuits have been contemplated by industry over the years in order to attempt to maximise power supply efficiency whilst reducing the number of components and minimising power losses.
A traditional manner of arranging a single phase PFC booster circuit relied upon a bridge rectifier device to rectify the AC mains supply into a continually changing DC voltage source.
For example, as discussed in the paper “Performance Evaluation of bridgeless PFC Boost Rectifiers” by Huber et al, IEEE TRANSACTIONS ON POWER ELECTRONICS, 2008, VOL 23; Issue 3, pages 1381-1390, conventional PFC booster circuits include full wave rectifiers consisting of four diode elements. An inductive element is provided in series, while a capacitive element is provided in parallel across the output of the rectifier output. A switchable power transistor is controlled to store energy in the inductive element and transfer that stored energy to the capacitive element.
A problem associated with such arrangements is the typical approximate 1V forward voltage drop across the full wave rectifier diodes, which significantly reduces the efficiency of the circuit. That is, during one half cycle of the AC mains supply, a voltage drop occurs across two diodes resulting in an approximate 1% energy loss for high line mains voltage operations and 2% energy loss for low line mains voltage operations.
Bridgeless PFC booster circuits have been developed in an attempt to reduce losses across the diodes of the rectifier section of the circuit. However, the various circuits developed have notable limitations, such as the high amount of switching noise presented to the mains supply, or the need to include two separate boost inductors.
An object of the present invention is to provide a PFC booster circuit that includes switchable power transistors to switch the circuit between a flyback and forward state to store energy in, and release energy from, an inductor element for storage in a capacitor element.
A further object of the present invention is to provide a PFC booster circuit arranged to minimise voltage drops across system components to increase energy efficiency.
A further object of the present invention is to provide a PFC booster circuit with a single inductive element.
Each object is to be read disjunctively with the object of at least providing the public with a useful choice.
The present invention aims to overcome, or at least alleviate, some or all of the afore-mentioned problems.